STABILITY OF STRANGE STARS (SS) DERIVED FROM A REALISTIC EQUATION OF STATE

A realistic EOS (equation of state) leads to strange stars (ReSS) which are compact in the mass–radius (M–R) plot, close to the Schwarzschild limiting line.1 Many of the observed stars fit in with this kind of compactness, irrespective of whether they are X-ray pulsars, bursters or soft γ repeaters or even radio pulsars. We point out that a change in the radius of a star can be small or large, when its mass is increasing and this depends on the position of a particular star on the M–R curve. We carry out a stability analysis against radial oscillations and compare with the EOS of other SS models. We find that the ReSS is stable and an M–R region can be identified to that effect.

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Equation of state of strange stars with admissible dark matter: Derivation from galactic rotational curves

Astronomische Nachrichten ◽

10.1002/asna.202113925 ◽

2021 ◽

Vol 342 (1-2) ◽

pp. 310-314

Author(s):

Moisés Razeira ◽

Fabio Köpp ◽

Guilherme Volkmer ◽

Magno Machado ◽

Dimiter Hadjimichef ◽

...

Keyword(s):

Dark Matter ◽

Equation Of State ◽

Strange Stars

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A New View on Young Pulsars in Supernova Remnants: Slow, Radio-quiet & X-ray Bright

International Astronomical Union Colloquium ◽

10.1017/s0252921100061017 ◽

2000 ◽

Vol 177 ◽

pp. 699-702 ◽

Cited By ~ 2

Author(s):

E. V. Gotthelf ◽

G. Vasisht

Keyword(s):

Magnetic Field ◽

Neutron Stars ◽

Supernova Remnants ◽

Simple Explanation ◽

Crab Pulsar ◽

Radio Pulsars ◽

Substantial Fraction ◽

Subsequent Evolution ◽

X Ray ◽

Field Decay

AbstractWe propose a simple explanation for the apparent dearth of radio pulsars associated with young supernova remnants (SNRs). Recent X-ray observations of young remnants have revealed slowly rotating (P∼ 10s) central pulsars with pulsed emission above 2 keV, lacking in detectable radio emission. Some of these objects apparently have enormous magnetic fields, evolving in a manner distinct from the Crab pulsar. We argue that these X-ray pulsars can account for a substantial fraction of the long sought after neutron stars in SNRs and that Crab-like pulsars are perhaps the rarer, but more highly visible example of these stellar embers. Magnetic field decay likely accounts for their high X-ray luminosity, which cannot be explained as rotational energy loss, as for the Crab-like pulsars. We suggest that the natal magnetic field strength of these objects control their subsequent evolution. There are currently almost a dozen slow X-ray pulsars associated with young SNRs. Remarkably, these objects, taken together, represent at least half of the confirmed pulsars in supernova remnants. This being the case, these pulsars must be the progenitors of a vast population of previously unrecognized neutron stars.

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Radio pulsars observed at X-ray energies by the X-ray timing explorer

Advances in Space Research ◽

10.1016/s0273-1177(98)00130-6 ◽

1998 ◽

Vol 22 (7) ◽

pp. 981-986

Author(s):

L.E. Peterson ◽

D. Marsden ◽

P. Blanco ◽

D.E. Gruber ◽

W.A. Heindl ◽

...

Keyword(s):

Radio Pulsars ◽

X Ray

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Quadrupole moments of rotating compact stars

Proceedings of the International Astronomical Union ◽

10.1017/s1743921312024787 ◽

2012 ◽

Vol 8 (S291) ◽

pp. 536-536

Author(s):

Martin Urbanec ◽

John Miller ◽

Zdenek Stuchlik

Keyword(s):

Neutron Star ◽

Equation Of State ◽

Neutron Stars ◽

Strange Star ◽

Compact Stars ◽

Quadrupole Moments ◽

Strange Stars

AbstractWe present quadrupole moments of rotating neutron and strange stars calculated using standard Hartle Thorne approach. We demonstrate differences between neutron and strange star parameters connected with quadrupole moments and how this parameters could be, in the case of neutron stars, approximated almost independently on neutron star equation of state.

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Are radio pulsars strange stars ?

Astronomy and Astrophysics ◽

10.1051/0004-6361:20010891 ◽

2001 ◽

Vol 375 (2) ◽

pp. 405-410 ◽

Cited By ~ 10

Author(s):

R. C. Kapoor ◽

C. S. Shukre

Keyword(s):

Radio Pulsars ◽

Strange Stars

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Thermal equation-of-state of osmium: a synchrotron X-ray diffraction study

Journal of Physics and Chemistry of Solids ◽

10.1016/j.jpcs.2004.08.045 ◽

2005 ◽

Vol 66 (5) ◽

pp. 706-710 ◽

Cited By ~ 13

Author(s):

G.A. Voronin ◽

C. Pantea ◽

T.W. Zerda ◽

L. Wang ◽

Y. Zhao

Keyword(s):

Equation Of State ◽

Diffraction Study ◽

X Ray Diffraction ◽

Thermal Equation ◽

X Ray ◽

Thermal Equation Of State

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Thermal Analysis, Compressibility, and Decomposition of Synthetic Bastnäsite-(La) to Lanthanum Oxyfluoride

Minerals ◽

10.3390/min10030212 ◽

2020 ◽

Vol 10 (3) ◽

pp. 212

Author(s):

Richard L. Rowland ◽

Barbara Lavina ◽

Kathleen E. Vander Kaaden ◽

Lisa R. Danielson ◽

Pamela C. Burnley

Keyword(s):

High Temperature ◽

Equation Of State ◽

Ambient Temperature ◽

Evolved Gas Analysis ◽

Ambient Pressure ◽

Basic Material ◽

X Ray Diffraction ◽

Scanning Calorimetry ◽

Thermal Equation ◽

X Ray

Understanding basic material properties of rare earth element (REE) bearing minerals such as their phase stability and equations of state can assist in understanding how economically viable deposits might form. Bastnäsite is the most commonly mined REE bearing mineral. We synthesized the lanthanum-fluoride end member, bastnäsite-(La) (LaCO3F), and investigated its thermal behavior and decomposition products from 298 K to 1173 K under ambient pressure conditions through thermogravimetric analysis, differential scanning calorimetry, evolved gas analysis, and high temperature powder X-ray diffraction. We also investigated the compressibility of bastnäsite-(La) via single crystal X-ray diffraction in diamond anvil cells at an ambient temperature up to 11.3 GPa and from 4.9 GPa to 7.7 GPa up to 673 K. At ambient pressure, bastnäsite-(La) was stable up to 598 K in air, where it decomposed into CO2 and tetragonal γ-LaOF. Above 948 K, cubic α-LaOF is stable. High temperature X-ray diffraction data were used to fit the Fei thermal equation of state and the thermal expansion coefficient α298 for all three materials. Bastnäsite-(La) was fit from 298 K to 723 K with V0 = 439.82 Å3, α298 = 4.32 × 10−5 K−1, a0 = −1.68 × 10−5 K−1, a1 = 8.34 × 10−8 K−1, and a2 = 3.126 K−1. Tetragonal γ-LaOF was fit from 723 K to 948 K with V0 = 96.51 Å3, α298 = 2.95×10−4 K−1, a0 = −2.41×10−5 K−1, a1 = 2.42×10−7 K−1, and a2 = 41.147 K−1. Cubic α-LaOF was fit from 973 K to 1123 K with V0 = 190.71 Å3, α298 = −1.12×10−5 K−1, a0 = 2.36×10−4 K−1, a1 = −1.73 × 10−7 K−1, and a2 = −17.362 K−1. An ambient temperature third order Birch–Murnaghan equation of state was fit with V0 = 439.82 Å3, K0 = 105 GPa, and K’ = 5.58.

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Thermal X-ray emission identified from the millisecond pulsar PSR J1909–3744

Astronomy and Astrophysics ◽

10.1051/0004-6361/201732040 ◽

2019 ◽

Vol 627 ◽

pp. A141 ◽

Cited By ~ 2

Author(s):

N. A. Webb ◽

D. Leahy ◽

S. Guillot ◽

N. Baillot d’Etivaux ◽

D. Barret ◽

...

Keyword(s):

Neutron Star ◽

Equation Of State ◽

Thermal Emission ◽

Black Body ◽

Millisecond Pulsar ◽

Distance Measurements ◽

Millisecond Pulsars ◽

X Ray ◽

Link Type

Context. Pulsating thermal X-ray emission from millisecond pulsars can be used to obtain constraints on the neutron star equation of state, but to date only five such sources have been identified. Of these five millisecond pulsars, only two have well-constrained neutron star masses, which improve the determination of the radius via modelling of the X-ray waveform. Aims. We aim to find other millisecond pulsars that already have well-constrained mass and distance measurements that show pulsed thermal X-ray emission in order to obtain tight constraints on the neutron star equation of state. Methods. The millisecond pulsar PSR J1909–3744 has an accurately determined mass, M = 1.54 ± 0.03 M⊙ (1σ error) and distance, D = 1.07 ± 0.04 kpc. We analysed XMM-Newton data of this 2.95 ms pulsar to identify the nature of the X-ray emission. Results. We show that the X-ray emission from PSR J1909–3744 appears to be dominated by thermal emission from the polar cap. Only a single component model is required to fit the data. The black-body temperature of this emission is $ {kT}=0.26^{0.03}_{0.02} $ keV and we find a 0.2–10 keV un-absorbed flux of 1.1 × 10−14 erg cm−2 s−1 or an un-absorbed luminosity of 1.5 × 1030 erg s−1. Conclusion. Thanks to the previously determined mass and distance constraints of the neutron star PSR J1909–3744, and its predominantly thermal emission, deep observations of this object with future X-ray facilities should provide useful constraints on the neutron star equation of state.

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The Galactic Pulsar Population and Neutron Star Birth

Symposium - International Astronomical Union ◽

10.1017/s0074180900160516 ◽

1987 ◽

Vol 125 ◽

pp. 67-78

Author(s):

Ramesh Narayan

Keyword(s):

Angular Momentum ◽

Neutron Star ◽

Binary Systems ◽

Magnetic Coupling ◽

Scale Height ◽

High Magnetic Fields ◽

Radio Pulsars ◽

X Ray ◽

The Galaxy ◽

Low Mass

The radio pulsars in the Galaxy are found predominantly in the disk, with a scale height of several hundred parsecs. After allowing for pulsar velocities, the data are consistent with the hypothesis that single pulsars form from massive stellar progenitors. The number of active single pulsars in the Galaxy is ∼ 1.5 × 105, and their birthrate is 1 per ∼ 60 yrs. There is some evidence that many single pulsars, particularly those with high magnetic fields, are born spinning slowly, with initial periods ∼ 0.5–1s. This could imply an origin through binary “recycling” followed by orbit disruption, or might suggest that the pre-supernova stellar core efficiently loses angular momentum to the envelope through magnetic coupling. The birthrate of binary radio pulsars, particularly of the millisecond variety, seems to be much larger than previous estimates, and might suggest that these systems do not originate in low mass X-ray binary systems.

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